New England Distribution

Non-native: introduced
(intentionally or
unintentionally); has become naturalized.

County documented: documented
to exist in the county by
evidence (herbarium specimen, photograph). Also covers
those considered historical (not seen in 20 years).

State documented: never been
documented from the
county, but known from the state. May be present. Or,
may be restricted to a small area or a habitat (alpine,
marsh, etc.), so unlikely found in some
counties.

Note: when native and non-native
populations both exist in a county, only native status
is shown on the map.

North America Distribution

Facts About

Not reaching farther north than Pennsylvania in its native range, rough marsh-elder is non-native in New England, but a common annual elsewhere in North America. Like ragweed, it is a source of allergenic airborne pollen. Rough marsh-elder was apparently cultivated by prehistoric Native Americans (Scioto Hopewell) as a seed crop, based on archeological remains documenting increases in achene size by 2000 BC.

Habitat

Anthropogenic (man-made or disturbed habitats)

Characteristics

Habitat

terrestrial

New England state

Maine

Massachusetts

Leaf type

leaves are simple (i.e., lobed or unlobed but not separated into leaflets)

Leaf arrangement

alternate: there is one leaf per node along the stem

opposite: there are two leaves per node along the stem

Leaf blade edges

the edge of the leaf blade has teeth

Flower type in flower heads

the flower head has tubular disk flowers in the center and ray flowers, these often strap-shaped, around the periphery